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In the derivation for ρgh we consider the weight above a given area to give pressure but because of it pressure should only be in vertical direction why is it found in every direction possible and in every direction it is equal to ρgh, for two opposite nonvertical directions it could have taken any value since at the end Net force is zero in any direction.

user45838
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    It's the way liquids work. Take a tube of toothpaste. Squeeze it from the side. Toothpaste comes out top. How is that? How did sideways-force become up-force? – Mike Dunlavey Jul 19 '17 at 18:58
  • It's the only conclusion we could get from the obervations. We must say that pressure acts in all directions with a magnitude equal to $\rho g h$. Now, once we have discovered this, we can think about $why$ or the possible theories. So enjoy it! :) Nature is fascinating. – Khalid T. Salem Jul 19 '17 at 21:00

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It is because of microscopic bonds between molecules and generally the way fluids (liquids) work. When you apply force to the water what happens? Let's say you punch the water. The force you applied will spread in all directions through the water and your punch will simply be absorbed. Surely you will not "break" the water like you could if you hit a solid object. Why is that?

That's because water and solid objects have different types of intermolecular bonds and forces. Water has "hydrogen bond" which is responsible for the way it acts. Because water molecules constantly move, hidrogen bonds constantly break up and connect again to new water molecules, so you can't simply "break the water", it will simply find new water to connect to, or spread out in water drops but on molecular level, nothing changed.

Plexus
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